داوود زارع حقی

12 hybrides of tomato and their parents were evaluated for their response to drought stress in a randomized complete block design with three replications and three irrigation levels (FC, 60%FC, and 40%FC). The studied genotypes were including Kingstone, Petoearly, Bitstoik, LA1607, LA2656, LA2080 and LA1579. Experiments on crossing the genotypes, seedling production and field evaluation, were done in experimental greenhouses and experimental field of Ilam University in 2014-2016. The studied traits consisted of proline, MDA, peroxidase, catalase and ascorbate peroxidase, Relative Water Content (RWC), Chlorophyll a, b and total, electrolyte leakage, total yield, potential yield and single plant yield. The statistical analysis showed that drought stress significantly affected all assessed traits under drought condition. Increase in Proline and MDA content was observed in all genotypes under drought stress. The highest values of proline )31.93 µMgFW-1) was obtained under severe stress in Petoearly× LA2080. RWC, total yield, potential yield, single plant yield, Chlorophyll a, b, catalase and ascorbate peroxidase contents were reduced and proline, electrolyte leakage and peroxidase content were increased by increase in drought stress. Under severe drought stress, the highest amount of total yield (15.74 t.ha-1) was observed in LA2656×Petoearly hybrid, Petoearly line (19 t.ha-1) and LA1579 tester (32 t.ha-1).

To investigate the effects of substituting surface drip irrigation (DI) by subsurface drip-irrigation systems (SDI) on plant responses, a10 ha pistachio orchard with DI system located in Shahriar, Tehran province, was selected. Irrigation treatments including DI and SDI with saline water and DI with non-saline water (A) were established and plant responses were measured. The salinity distribution results showed that, in DI, at depth of 30-50 cm and distance of 70-100 cm, salts were accumulated. In SDI, salt accumulation was observed in surface layer and in distance of 60-80 cm from the tree. Based on all plant response indicators, treatment A showed significantly more favorable conditions. Unlike treatment A, there was no significant difference in the “canopy temperature” and “canopy–air temperature difference” between DI and SDI. By normalization of environmental-effects on foliage temperature, crop water stress index (CWSI) showed significant differences between DI and SDI treatments. Also, stomata conductance in SDI was significantly greater than DI. Additionally, treatment A had significantly the highest sap flow (SF). Based on SF measurement in 24 hour, there were no significant differences between DI and SDI irrigation systems, but the mean of this index for daylight time and midday, showed significant differences. With equal depth of irrigation water applied to DI and SDI and more favorable salinity distribution in root zone of SDI, this treatment leads to less water and salinity stress. Although the use of subsurface drip irrigation system requires long-term studies, but in view of the observed plant responses and in terms of soil salinity distribution, it is recommended to use SDI in pistachio trees.

12 single crosses (F1) achieved by combining four testers and three commercial lines of tomato were evaluated for their response to water deficit stress and the combining ability of yield and some yield components. The layout was split plots according to randomized complete block design with three replications and three irrigation levels (FC, 60%FC and 40%FC). Crossing among lines and testers, seedling production and field evaluation, were conducted in greenhouses and field of Ilam University during 2014-2016. The studied genotypes were L1: Bitstoik, L2: Kingstone, L3: Petoearly, as lines, and T1: LA1607, T2: LA2656, T3: LA2080 and T4: LA1579 as Testers. The studied traits consisted of total yield, potential yield, yield per plant, number of fruits per plant, plant height and days to 50% flowering. The analysis of variance indicated that significant differences existed among, genotypes, parents, parents vs. crosses, crosses, lines, testers and line × tester for all studied traits on both non- stress and water deficit stress, which showed a significant difference between general combining ability (GCA) of parents and specific combining ability (SCA) of hybrids. In general, the parental testers, LA2656 (T2), LA1607 (T1) and Line L1 (Bitstoik) were found to have the highest GCA for total yield and potential yield, and the number of fruits per plant in both conditions. The Petoearly×LA1579 in non- stress, Bitstoik× LA1607 and Kingstone×LA1579 in mild and severe-stresses had the highest SCA for total yield. Analysis of variance for combining ability manifested the predominance of dominance gene action for total yield, yield per plant and potential yield. The general combining ability (GCA) effects were generally found higher than SCA effects in terms of the agronomic traits. As a result, the low ratio of δ2A/ δ2D showed that non-additive effects controlled the studied traits.

This study was conducted to test the effect of essential oils of savory (Satureja hortensis), clove (Zyzigium aromaticum) at concentrations of 0, 250 or 500 mgL-1 with sucrose treatments at 0 or 2% on vase life of cut rose cv. “Velvet”.The experiment was conducted at 20±2oC, RH: 60-70% and 12µmolm-2s-1 light intensity with white fluorescent tubes under daily light period of 12h. This experiment was performed in a factorial experiment based on completely randomized design comprising eighteen treatments, three replications and 3 cut flowers in each vase for measuring vase life, relative fresh weight, solution uptake, chlorophyll contents. Chlorophyll fluorescence parameters were measured in each replicate. Results showed that 500mgL-1 of essential oils caused maintaining the vase life of cut flowers better than the rest of treatments. 250mgL-1 of essential oils increased chlorophyll index and solution uptake in comparison with other concentrations. Treatment of sucrose 2% could cause significantly more vase life, chlorophyll fluorescence and chlorophyll index compared to 0% sucrose treatment. Savory and clove essential oils at 500 and 250 mgL-1 concentrations caused a significantly higher relative fresh weight and a reduction in stomatal conductance.

Multidimensional nature of water flow, plant uptake, and high frequency of water application increase the complexity in modeling soil moisture dynamics from trickle irrigation. By determining soil hydraulic properties, parameters of root distribution model for pistachio trees in the field, evapotranspiration and inflow flux, soil moisture distribution was modeled using HYDRUS-2D model for surface (DI) and sub-surface drip irrigation (SDI) systems. Also, soil moisture content in the following days after irrigation was measured at different lateral and vertical distances from the tree by using Moisture Meter Profile Probe. Leaf stomatal conductance was used to test the model and parameterize water-stress response function. The h50 for pistachio tree, which represents the pressure head at which the water extraction rate is reduced by 50%, was calculated 4935 cm. HYDRUS outputs were compared with measured data in corresponding locations, and values ofME, RMSE, E and R2 statistics were obtained -0.002, 0.02, 0.7, 0.741 for DI and 0.006, 0.021, 0.761, and 0.794 for SDI respectively. The calculated transpiration by HYDRUS showed high correlation with stomatal conductance, especially in SDI. Based on plant measurements and HYDRUS results, root water uptake in SDI was significantly more than DI. Therefore, using SDI systems, by decreasing evaporation, saves more water and increases irrigation efficiency. The calculated root water uptake and measured stomatal conductance for the pistachio trees revealed that soil moisture perfectly supports plants until four days after irrigation. Thus, by decreasing irrigation interval in the field, maximum potential of drip irrigation systems can be achieved.

The range of soil water content where plant growth is least limited by water potential, soil aeration or mechanical resistance is called least limiting water range (LLWR). This study evaluated the values of LLWR determined according to the procedures proposed by da Silva et al. with those calculated on the basis of sunflower plant (Helianthus annuus L) response (LLWRP). In both methods LLWR is taken as the difference between the two soil moisture limits designated as upper (θUL) and lower (θLL). In the first method, the two limits are determined basically from the soil moisture and soil resistance characteristic curves, almost overlooking the plant type and its particular needs or behaviors. In the second method, as proposed in this research, the two limits are determined based on the stomatal response in a sandy clay loam soil packed into PVC tubes (called pots hereafter) with 30 cm diameter and 70 cm height at three compaction levels (soil bulk density equal to 1.75, 1.55 and 1.35 Mg.m-3) designated as D1, D2 and D3. Each pot was planted with three pre-soaked sunflower seeds and pots were kept under optimum condition until onset of the flowering stage. At this time two successive drying cycles were imposed and soil moisture and midday stomatal conductance were routinely measured. LLWRP were computed on the basis of relationship between soil matric suction and stomatal conductance. Results showed that on the basis of stomatal conductance behavior water uptake began at the soil matric suctions of 44, 16, 60 and continued up to 17394,31614, 39983 cm in D1, D2 and D3 treatments, respectively. Appreciable differences were observed between LLWR and LLWRP particularly when the lower limit moisture suction (equivalent to θUL for LLWR) was set at 330 cm (LLWR330). LLWR330 values of 0.148, 0.147 and 0.080 cm3cm-3 were obtained for D1, D2, D3 treatments, respectively, which were 51, 49 and 63 percent lower than the corresponding LLWRP values. This differences imply that the two moisture limits (θUL and θLL) proposed by da Silva et al. may not be applied indiscriminately for all plants and thus need to be modified according to plant needs or responses.

Integral water capacity (IWC) is the integral of differential water capacity functions in the range of 0 to infinity soil matric potential multiplied [H1] by weighting functions each taking into account the effect of varioussoil limitations that may develop at a given soil matric potential domain and restrict soil water availability to plant roots. The domains selected for development of weighting functions in most studies have seldom been based on plant response, but rather arbitrary. The purpose of this study was implementing midday green leaf temperature (TL) as a plant-response-based variable to compute integral water capacity. For this purpose, a sandy clay loam soil passed through 4.76 mm sieve was evenly compacted to three bulk densities of D1=1.35, D2=1.55, and D3=1.75 g cm-3, each replicated thrice, in PVC tubes (called pots hereafter) with 30 cm diameter and 70 cm height. Sunflower (Helianthus Annuus L) seedlings were planted in the pots and, after their full establishment, two periods of wetting and drying cycles were imposed. By monitoring daily soil moisture content at the three depths in the pots and converting them to soil moisture suctions along with the midday TL measurements, a plant-response-based weighting function was developed and integral water capacity (IWCP) was computed. Integral water capacity (designated as IWCG) was also computed by adopting the weighting functions proposed by Groenevelt et al. IWCP and IWCG in D1 treatment were obtained as 0.187 and 0.229 cm3cm-3, respectively. At the highly compacted D3 treatment, the corresponding values diminished to 0.152 and .038, respectively, equivalent to 19% and 84% reduction in soil water availability and reflecting the dominant effect of soil compaction on water availability. Averaged over the three compaction levels, IWCP and IWCG were 0.169 and 0.14 cm3cm-3,indicating that water availability determined on the plant response basis was 17% greater than that predicted by IWCG. This difference and over-susceptibility (84%) of IWCG to soil compaction imply that the soil suction domains proposed for the various soil limitations and the experimental relations employed in Groenevelt et al. approach to quantify their restricting effects as weighing functions need to be modified according to each particular plant needs or response.

Most plants encounter with different environmental stresses during their life cycle. Water deficit is one of the stresses that negatively affect the growth and yield of many agricultural crops such as members of citrus family. Higher plants developed several physiological and biochemical adaptation systems that give them a chance to survive and let them to escape from water deficit stress. In this research the effect of Nitric Oxide, as a stress modulator, on citrus plants was investigated. A trial was conducted as factorial with randomized complete blocks design in three replications on three species of citrus including Poncirus, Swingle citrumelo and Carrizo citrange. There were also drought stress treatments in three levels (FC, 30% FC and 60% FC) and Sodium nitroprusside treatments, as a NO releasing compound, in three levels (0, 0.5 and 1 mM). Some physiological factors such as chlorophyll fluorescence, stomatal conductance, leaf water potential and leaf relative water content were measured. Also, some biochemical factors such as DPPH and the contents of phenols and malondialdehyde were investigated. The results showed that drought stress, decreased leaf water potential, stomatal conductance, relative water content and Fv/Fm significantly. Some biochemical factors such as DPPH, phenols and malondialdehyde activity increased during drought stress. Application of sodium nitroprusside, modulated the destructive effects of drought stress specially with the concentration of 1 mM.

In order to study the effects of hydrogen peroxide (0¡ 100¡ 300¡ 500 and 700 µM) and sucrose (0 and 2%) on the vase life and water relations of cut rose flower cv. Candy¡ a factorial experiment was carried out based on a completely randomized design with 3 replications. In this experiment parameters of vase life¡ solution uptake¡ stem relative fresh weight¡ leaf stomatal conductivity¡ leaf relative water content and membrane stability index of petal cells were evaluated. Application of 500 and 700 µM hydrogen peroxide increased significantly vase life of cut rose stem in comparison with other treatments so that 700 µM increased vase life 12 days compared to control. The effect of 700µM sucrose 2% had a most significant effect on increasing solution uptake and stem relative fresh weight compared to other treatments. Leaf stomatal conductance decreased by increasing hydrogen peroxide concentration. Lowest amount was related to 500 and 700 µM of hydrogen peroxide treatments alone and with 2% sucrose. The highest amount of leaf relative water content and petal cells membrane stability index was related to H2O2 700µM treatment. In conclusion¡ the results showed that hydrogen peroxide treatment alone at highest concentration (700µM) increased vase life and with sucrose 2% improved solution uptake and stem relative fresh weight¡ as well as it caused a decreasing effect on leaf stomatal conductivity with keeping leaf relative water content and petal cells membrane stability index.